1. Field of the Invention
The present invention relates to a liquid ejection head mounted in a liquid ejection apparatus adapted to eject liquid.
2. Description of the Related Art
At present, on a printing element substrate mounted in a liquid ejection head, multiple connecting terminals for connecting to an electric wiring substrate of the liquid ejection head are provided. The connecting terminals provided on the printing element substrate have connecting members made of Au, and the electric wiring substrate has inner leads for corresponding connecting terminals, respectively. The wiring substrate and the printing element substrate are connected to each other through the connecting members and the inner leads. The electric wiring substrate has outer leads on the side opposite to the inner leads, which are connected to an electric wiring member including connecting terminals for connecting to a liquid ejection apparatus.
To connect the connecting terminals of the printing element substrate to corresponding inner leads, a single point bonding method is available. When performing single point bonding, an inner lead and a corresponding connecting terminal are applied with an ultrasonic wave and a load using a tool. To make it possible to stably connect the multiple inner leads, conditions should be established.
Japanese Patent Laid-Open No. H10-230611(1998) describes an example of single point bonding of one inner lead to one connecting terminal. To make it possible to perform the bonding under the same conditions, all inner leads are formed so as to have the same line width.
Recently, in a liquid ejection apparatus, a printing element substrate is increased in length to improve printing speed. Also, in order to efficiently drive energy generating elements for ejecting liquid, voltage is increased for the driving. The increases in length and voltage increase current that flows through a liquid ejection head to drive the energy generating elements.
As described, in the situation where the current flowing through the liquid ejection head is increased, increasing a current amount without changing a line width of an electric wiring substrate may increase a heat generation amount of the electric wiring substrate to impair reliability. A possible method to overcome such impairment is to increase the line width correspondingly to the increased current amount to suppress the heat generation. In such a case, it is necessary to increase the width of inner leads so as to correspond to the current amount as well.
Among the inner leads, leads for logic applied with small current are not required to have increased width, and therefore configured to have different width from that of leads for energy generating element driving current.
As described, in the case where line width is different between the leads for logic and the leads for energy generating element driving current, the connection (bonding) between the inner leads and wiring lines of an electric wiring substrate under the same conditions fails in stable bonding. To stably perform the bonding, joining conditions such as bonding tool width and load should be changed for each of the lead widths. In addition, bonding targets to be bonded under the same conditions are typically simultaneously bonded, and therefore bonding should be performed for each set of bonding conditions, i.e., bonding should be performed several times. For this reason, an extra tool traveling distance is required, increasing a bonding time.